We hypothesize that prostate cancer cells metabolize their arachidonic acid (AA) stores via cyclooxygenases[unreadable] (COX), 5-lipoxygenase (LOX), or 15-LOX-1 to prostaglandin (PG)E2, 5-hydroxy-eicosatetraenoate (5-HETE),[unreadable] or 12-HETE, respectively, that the production of one or more of these eicosanoids is essential for prostate[unreadable] cancer cell proliferation, and that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) interfere[unreadable] with the oxygenases to inhibit this proliferation. We have developed a model relevant to these hypotheses.[unreadable] Pten[loxp/loxp]xPB-Cre4 (Pten-/-) mice develop prostate lesions that progress from hyperplasia to cancer. This[unreadable] progression is speeded in mice fed an n-6 diet (rich in AA and AA precursors) and suppressed in mice fed an[unreadable] n-3 diet (rich in EPA and DHA). We will test our hypotheses using human and mouse prostate cells in vitro[unreadable] and our animal model in vivo with three Specific Aims. These Aims are designed to show that:[unreadable] 1) Human prostate cancer cell lines and Pten-/-' mouse prostate cells use 5-LOX, COX-1/2, and/or 15-LOX-1[unreadable] to make 5-HETE, PGE2, and/or 12-HETE to promote their own proliferation in vitro.[unreadable] 2) EPA and DHA interfere with one or more of the oxygenases to block eicosanoid production and thereby[unreadable] inhibit the proliferation of human prostate cancer cell lines and Pten-/- mouse prostate cells in vitro.[unreadable] 3) The n-3 diet similarly interferes with one or more of the oxygenases to block eicosanoid production and[unreadable] the malignant growth of the prostate gland and thereby improves survival in Pten-/- mice.[unreadable] Previous studies have measured AA metabolites in prostate cancer cell lines in vitro but preloaded the cells[unreadable] with AA to detect the metabolites. AA preloading would pervert any investigation into the effects of EPA,[unreadable] DHA, and the n-3 diet on AA metabolism. We have established a reversed-phase high performance liquid[unreadable] chromatography/electrospray ionization tamdem mass spectroscopy method and with it detected for the first[unreadable] time PGE2, 5-HETE, and 12-HETE in resting PC-3 cells not preloaded with AA. This represents a significant[unreadable] advance that will allow us to characterize the metabolites of AA, EPA, and DHA made by prostate cells and[unreadable] tissues in vitro and in vivo. We are therefore positioned to test our hypotheses and thereby to identify the[unreadable] molecular targets and define the mechanism for the anti-cancerous effects of EPA, DHA, and the fish oil[unreadable] diets which contain these fatty acids.